THAI MASSAMAN LAMB CURRY

2 tbsp sunflower oil • 2 x 400ml cans Thai Taste Coconut Milk • 100g massaman curry paste • 800g lamb leg or shoulder, sliced • 3 tbsp smooth peanut butter • 350g baby new potatoes, quartered • 200ml fresh chicken stock • 1 red onion, thickly sliced • 2 tbsp tamarind paste • 2 tbsp light brown soft sugar • 2½ tbsp Thai Taste Fish Sauce, plus extra to serve • 1 red chilli, deseeded and sliced • 3 tbsp roasted peanuts, roughly chopped • small handful Thai basil • 2 limes, cut into wedges